Do you think the stock market is an "efficient market"?

MNSL answered one year ago …

In the real world, markets cannot be absolutely efficient or wholly inefficient. It might be reasonable to see markets as essentially a mixture of both, wherein daily decisions and events cannot always be reflected immediately into a market. If all participants were to believe that the market is efficient, no one would seek extraordinary profits, which is the force that keeps the wheels of the market turning. Please see following web links:

http://www.investopedia.com/articles/02/101502.asp

When money is put into the stock market, it is done with the aim of generating a return on the capital invested. Many investors try not only to make a profitable return, but also to outperform, or beat, the market.

However, market efficiency - championed in the efficient market hypothesis (EMH) formulated by Eugene Fama in 1970, suggests that at any given time, prices fully reflect all available information on a particular stock and/or market. Thus, according to the EMH, no investor has an advantage in predicting a return on a stock price because no one has access to information not already available to everyone else. (To read more on behavioral finance, see Taking A Chance On Behavioral Finance, Understanding Investor Behavior and Mad Money ... Mad Market?)

The Effect of Efficiency: Non-Predictability
The nature of information does not have to be limited to financial news and research alone; indeed, information about political, economic and social events, combined with how investors perceive such information, whether true or rumored, will be reflected in the stock price. According to EMH, as prices respond only to information available in the market, and, because all market participants are privy to the same information, no one will have the ability to out-profit anyone else.

In efficient markets, prices become not predictable but random, so no investment pattern can be discerned. A planned approach to investment, therefore, cannot be successful.

This "random walk" of prices, commonly spoken about in the EMH school of thought, results in the failure of any investment strategy that aims to beat the market consistently. In fact, the EMH suggests that given the transaction costs involved in portfolio management, it would be more profitable for an investor to put his or her money into an index fund.

Anomalies: The Challenge to Efficiency
In the real world of investment, however, there are obvious arguments against the EMH. There are investors who have beaten the market - Warren Buffett, whose investment strategy focuses on undervalued stocks, made millions and set an example for numerous followers. There are portfolio managers who have better track records than others, and there are investment houses with more renowned research analysis than others. So how can performance be random when people are clearly profiting from and beating the market?

Counter arguments to the EMH state that consistent patterns are present. Here are some examples of some of the predictable anomalies thrown in the face of the EMH: the January effect is a pattern that shows higher returns tend to be earned in the first month of the year; "blue Monday on Wall Street" is a saying that discourages buying on Friday afternoon and Monday morning because of the weekend effect, the tendency for prices to be higher on the day before and after the weekend than during the rest of the week.

Studies in behavioral finance, which look into the effects of investor psychology on stock prices, also reveal that there are some predictable patterns in the stock market. Investors tend to buy undervalued stocks and sell overvalued stocks and, in a market of many participants, the result can be anything but efficient.

Paul Krugman, MIT economics professor, suggests that because of the mass mentality of the trendy, short-term shareholder, investors pull in and out of the latest and hottest stocks. This results in stock prices being distorted and the market being inefficient. So prices no longer reflect all available information in the market. Prices are instead being manipulated by profit seekers.

The EMH Response
The EMH does not dismiss the possibility of anomalies in the market that result in the generation of superior profits. In fact, market efficiency does not require prices to be equal to fair value all of the time. Prices may be over- or undervalued only in random occurrences, so they eventually revert back to their mean values. As such, because the deviations from a stock's fair price are in themselves random, investment strategies that result in beating the market cannot be consistent phenomena.

Furthermore, the hypothesis argues that an investor who outperforms the market does so not out of skill but out of luck. EMH followers say this is due to the laws of probability: at any given time in a market with a large number of investors, some will outperform while other will remain average.

How Does a Market Become Efficient?
In order for a market to become efficient, investors must perceive that a market is inefficient and possible to beat. Ironically, investment strategies intended to take advantage of inefficiencies are actually the fuel that keeps a market efficient.

A market has to be large and liquid. Information has to be widely available in terms of accessibility and cost and released to investors at more or less the same time. Transaction costs have to be cheaper than the expected profits of an investment strategy. Investors must also have enough funds to take advantage of inefficiency until, according to the EMH, it disappears again. Most importantly, an investor has to believe that she or he can outperform the market.

Degrees of Efficiency
Accepting the EMH in its purest form may be difficult; however, there are three identified classifications of the EMH, which are aimed at reflecting the degree to which it can be applied to markets.
1. Strong efficiency - This is the strongest version, which states that all information in a market, whether public or private, is accounted for in a stock price. Not even insider information could give an investor an advantage.

2. Semi-strong efficiency - This form of EMH implies that all public information is calculated into a stock's current share price. Neither fundamental nor technical analysis can be used to achieve superior gains.

3. Weak efficiency - This type of EMH claims that all past prices of a stock are reflected in today's stock price. Therefore, technical analysis cannot be used to predict and beat a market.

Conclusion
EMH propagandists will state that profit seekers will, in practice, exploit whatever abnormally exists until it disappears. In instances such as the January effect (a predictable pattern of price movements), large transactions costs will most likely outweigh the benefits of trying to take advantage of such a trend.

In the real world, markets cannot be absolutely efficient or wholly inefficient. It might be reasonable to see markets as essentially a mixture of both, wherein daily decisions and events cannot always be reflected immediately into a market. If all participants were to believe that the market is efficient, no one would seek extraordinary profits, which is the force that keeps the wheels of the market turning.

In the age of information technology (IT), however, markets all over the world are gaining greater efficiency. IT allows for a more effective, faster means to disseminate information, and electronic trading allows for prices to adjust more quickly to news entering the market. However, while the pace at which we receive information and make transactions quickens, IT also restricts the time it takes to verify the information used to make a trade. Thus, IT may inadvertently result in less efficiency if the quality of the information we use no longer allows us to make profit-generating decisions.

http://www.investopedia.com/terms/e/efficientmarkethypothesis.asp

An investment theory that states that it is impossible to "beat the market" because stock market efficiency causes existing share prices to always incorporate and reflect all relevant information. According to the EMH, this means that stocks always trade at their fair value on stock exchanges, making it impossible for investors to either purchase undervalued stocks or sell stocks for inflated prices. As such, it should be impossible to outperform the overall market through expert stock selection or market timing, and that the only way an investor can possibly obtain higher returns is by purchasing riskier investments.

Although it is a cornerstone of modern financial theory, the EMH is highly controversial and often disputed. Believers argue it is pointless to search for undervalued stocks or to try to predict trends in the market through either fundamental or technical analysis.

Meanwhile, while academics point to a large body of evidence in support of EMH, an equal amount of dissension also exists. For example, investors such as Warren Buffet have consistently beaten the market over long periods of time, which by definition is impossibility according to the EMH. Detractors of the EMH also point to events such as the 1987 stock market crash (when the DJIA fell by over 20% in a single day) as evidence that stock prices can seriously deviate from their fair values.